Field of the Invention
The present invention relates to a teleconverter for achieving a lens system having a focal length longer than a focal length of a master lens apparatus, by mounting the master lens apparatus, and an image pickup system using the teleconverter.
Description of the Related Art
A rear teleconverter having a mount portion for a master lens apparatus, and a mount portion corresponding to each of mount portions of an image pickup apparatus main-body, in which, a converter lens portion is held between the master lens apparatus and the image pickup apparatus main-body via these mount portions, and which elongates a focal length of the overall lens system, has hitherto been known.
Here, it is preferable to include a lens unit in which, three lenses are cemented, including in order from an object side to an image side, a first lens having a negative refractive power, a second lens having a positive refractive power, and a third lens having a negative refractive power, at an intermediate portion of the converter lens section, as such an arrangement enables to reduce an effect of mutual decentering of lenses.
As a teleconverter which includes the lens unit in which, three lenses are cemented, at the intermediate portion of the converter lens section in such manner, teleconverters disclosed in Japanese Patent Application Laid-open Publication Nos. 2004-226648, 2005-107261, 2009-080176, 2011-081111, 2013-235217, and 2013-250291 are available.